A modular illuminating device comprises at least one frame (1) with the front elastic catches (2) for securing a transparent cover (4) to the frame (1), and the rear elastic catches (3) for fixing the frame (1) to a printed-circuit board (5) with at least one printed circuit module (6) and at least one light-emitting diode module (7) on its front side. The printed-circuit board (5) has multiple equally spaced assemblies comprised of the printed circuit modules (6) and LED modules (7), arranged in a row, or a rectangular matrix, or a honeycomb structure. The printed-circuit board (5) comprises an aluminum radiator, preferably an aluminum plate (8), placed at its rear side.